Meloni Muir

Influence of Glucocorticoids on Human Osteoclast Generation and Activity

Using human peripheral blood mononuclear cells as osteoclast precursors, we showed that dexamethasone stimulated osteoclast generation at a pharmacological concentration but did not affect the life span of human osteoclasts. Dexamethasone also dose‐dependently increased signals for osteoclastogenesis.

Functional α1‐ and β2‐adrenergic receptors in human osteoblasts

Central (hypothalamic) control of bone mass is proposed to be mediated through β2‐adrenergic receptors (β2‐ARs). While investigations in mouse bone cells suggest that epinephrine enhances both RANKL and OPG mRNA via both β‐ARs and α‐ARs, whether α‐ARs are expressed in human bone cells is controversial. The current study investigated the expression of α1‐AR and β2‐AR mRNA and protein and the functional role of adrenergic stimulation in human osteoblasts (HOBs). Expression of α1B‐ and β2‐ARs was examined by RT‐PCR, immunofluorescence microscopy and Western blot (for α1B‐ARs). Proliferation in HOBs was assessed by 3H‐thymidine incorporation and expression of RANKL and OPG was determined by quantitative RT‐PCR. RNA message for α1B‐ and β2‐ARs was expressed in HOBs and MG63 human osteosarcoma cells. α1B‐ and β2‐AR immunofluorescent localization in HOBs was shown for the first time by deconvolution microscopy. α1B‐AR protein was identified in HOBs by Western blot. Both α1‐agonists and propranolol (β‐blocker) increased HOB replication but fenoterol, a β2‐agonist, inhibited it. Fenoterol nearly doubled RANKL mRNA and this was inhibited by propranolol. The α1‐agonist cirazoline increased OPG mRNA and this increase was abolished by siRNA knockdown of α1B‐ARs in HOBs. These data indicate that both α1‐ARs and β2‐ARs are present and functional in HOBs. In addition to β2‐ARs, α1‐ARs in human bone cells may play a role in modulation of bone turnover by the sympathetic nervous system. J. Cell. Physiol. 220: 267–275, 2009.

Biomimetic Hydroxyapatite Micro-Tube Tissue Scaffold

The aim of this study was to fabricate a micro-tube scaffold using a biomimetic method (immersion in Simulated Body Fluid, SBF) to coat apatite on cotton fibres. The cotton fibres were first pre-treated using a phosphorylation technique and then apatite crystals were deposited on the fibres by immersing in SBF. Micro-tubes were then formed by burning out the cotton fibres at various temperatures between 950-1250°C. The scaffolds were fabricated by compaction of the micro-tubes in a mould. The compacted micro-tubes were then sintered at various temperatures between 900-1200°C. The biocompatibility and the effects of the surface morphology of scaffolds on cell coverage and proliferation were determined using osteoblast cell culture. The results showed that these scaddolds were biocompatible and able to support cell growth. Future studies include animal studies for biomimetic tissue scaffold as a bone filler substitute material.

Novel Calcium Phosphate Fibres from a Biomimetic Process: Manufacture and Cell Attachment

Biomimetic method has been used extensively to coat many materia ls in the attempt to make them bioactive. Using a biomimetic method, combustible fibres were coated with a c alcium phosphate apatite. Phosphorylation was employed as a pretreatment and simulated body fluid (SBF) as the growth solution. Burnout of the combustible fibres at varying te mperatures produced biomimetically coated calcium phosphate hollow fibres. There was g enerally increased sintering and crystallisation with increasing temperature. Cell studies of the sintered fibres showed successful cell adhesion of osteoblast cells. Results were prese nted with SEM, XRD and EDS. This research could lead to applications of calcium phosphate fibres in tis sue scaffolds and internal bandages, and possibly as composites. Introduction Biomimetic method has been used extensively to coat many material s in the attempt to make them bioactive. This method comprises two-steps of pre-treatment and deposi tion. Kokubo et al. in 1982 [1] developed apatite wollastonite (AW) glass-ceramic that exhi bited good bone bonding ability, with no foreign body infection, and was seen as a load bearing bioactive bone substitute. Kokubo et al. [2] completed tests in an acellular simulated body fluid. In 1991, it w as then found that any material and any shape could achieve a bioactive coating inc luding alumina, cotton and carbon [3]. M.R. Mucalo et al. [4] continued this work coating cellulose and cotton in 1993, bamboo was coated by S.H. Li et al. [5] and chitosan was coated by Y. Yokogawa et l. [6] in 1997. Thus a bioactive fibrous material using a biomimetic approach was a chieved. Using electrophoretic deposition to coat hydroxyapatite on carbon, I. Zhitomirsky [7] burnt out the c arbon to achieve a hollow hydroxyapatite fibre. With the background of both biomimetic coating a d burnout, the following paper will look at the experimental approach to coating cott on with a calcium phosphate apatite, and the burning out of the combustible substrate cotton to achieve calcium phosphate fi bres. Experimental Procedure Preparation of Calcium Phosphate Fibre Manufacture Phosphorylation Treated Cotton Phosphorylation of cotton samples were carried out following the prepara tion reported by Inagaki et al. [8]. Cotton pieces were placed in a round bottom flask equipped with a t hermometer, mechanical stirrer, condenser and N 2 gas inlet tube. Urea dissolved in dimethyl formamide (DMF) was added to the flask and heated to 130°C, upon which phosphorous acid (H 3PO3) was added and heated to 145°C. The reaction was allowed to reflux for thirty minutes . Cotton fibres were then washed repeatedly in distilled water and dried in an oven at 50°C. Ca(OH)2 Treatment The phosphorylated cotton was soaked (without stirring) in a saturated s olution of Ca(OH) 2 (pH ~ 11-12) in closed screw-top glass bottle for periods of up to 8 days. T he Ca(OH) 2 solution was Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 343-346 doi:10.4028/www.scientific.net/KEM.254-256.343